It is narrated from Hazrat Abu Huraira (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: When any one of you intends to pray, he should place something in front of him (as a sutrah). If he does not find anything, then he should set up a staff. And if he does not even have a staff, then he should draw a line. After that, if anything passes in front of him, it will not harm him.